What I understand is, you mean an edit history visible to public. At the moment I guess only mod/admin can see edit history, not sure though. Publicly it's not available however I think it should be publicly available too.  

I experienced the need for this when I had a hard time (I am still suffering) going on with a member. He kept changing his previous posts (without keeping reference most of the time) where he could easily correct his contents on the new comments. Editing older posts (which already responded based on your previous content) without reference actually can change the whole point of view of a conversation. It's mislead the new readers and they actually find it hard to get connection of the conversations.